The present disclosure relates to an image forming apparatus and a post-processing method. More particularly, the disclosure relates to an image forming apparatus and a post-processing method in which, when performing processing that includes punching processing and stapling processing, a sheet-bundle interval time can be optimized by utilizing a punching processing time and thereby makes it possible to decrease the processing time.
In a post-processing device (sheet processing device) including a stapler, which performs stapling processing on a sheet bundle placed on a predetermined processing tray, and which outputs the stapled sheets to a predetermined output tray, the interval between the last sheet of the sheet bundle which has been stapled and the first sheet of a subsequent sheet bundle is set to be a maximum time for performing stapling processing described in the specifications of the stapler.
In this manner, after stapling a sheet bundle on the processing tray and outputting the stapled sheet bundle to the output tray, a subsequent sheet is outputted to the processing tray. In this case, however, feeding the subsequent sheet does not start until the above-described maximum time has elapsed, thereby considerably decreasing the throughput of the post-processing device.
As a sheet processing device that can solve such a problem, the following sheet processing device (hereinafter referred to as a “first sheet processing device”) is known. The first sheet processing device includes a sheet loading unit on which outputted sheets are loaded, a stapler that staples a sheet bundle loaded on the sheet loading unit, and a stapling operation time measuring unit that measures the stapling operation time of the stapler. The first sheet processing device also includes a controller that controls the interval between a preceding sheet bundle and a subsequent sheet bundle, to be outputted to the sheet loading unit, by considering the stapling operation time measured by the stapling operation time measuring unit. With this configuration, the stapling operation time of the stapler is measured by the stapling operation time measuring unit. Accordingly, the stapling operation time, which may vary in accordance with the sheet size or the position of the stapler, can be measured in real time. Then, the first sheet processing device controls the interval between a preceding sheet bundle and a subsequent sheet to be outputted to the sheet loading unit in accordance with the stapling operation time, thereby making it possible to optimize the interval between the preceding sheet and the subsequent sheet. With this configuration, the efficiency in loading sheets on the sheet loading unit can be improved, and also, the throughput of the first sheet processing device can be enhanced.
A sheet processing device (hereinafter referred to as a “second sheet processing device”) is also known. The second sheet processing device includes a punching unit, that is located in a sheet feed path and punches a rear end of a sheet which is being fed, and a punching-unit moving unit that moves the punching unit in a direction intersecting with the sheet feed direction. The second sheet processing device also includes a sheet end detector that detects a side end of a sheet positioned in the sheet feed path, and a punching operation detector that detects that the punching unit is punching a sheet after moving from a punching-operation home position. Then, in the second sheet processing device, upon detection by the punching operation detector that the punching operation is finished, the punching-unit moving unit moves the punching unit in a direction intersecting with the sheet feed direction. With this configuration, when the punching unit is returned to the home position, after the punching operation detector has detected that the punching operation is finished, a standby operation for moving the punching unit to the home position in the direction intersecting with the sheet feed direction starts. With this operation, it is possible to decrease the sheet processing time and thereby to improve productivity in sheet processing.
The following image forming system is also known. The image forming system includes an image forming apparatus that outputs a recording sheet on which an image is formed to a post-processing device, and a plurality of post-processing devices interconnected to each other. Each of the post-processing devices has a path connected to a subsequent post-processing device. In this image forming system, post-processing can be performed on a recording sheet on which an image is formed by using one of the post-processing devices. In the image forming system, an image forming controller controls the sequentially switching between post-processing devices so that a set of recording sheets to be post-processed may be distributed to an associated post-processing device. The image forming controller determines the image forming standby time generated in the image forming apparatus between sets of recording sheets in accordance with the system configuration. With this configuration, in the image forming system including a plurality of interconnected post-processing devices and performing post-processing by using at least two of the post-processing devices, even if the system configuration is changed, control can be performed in accordance with the changed system configuration so that an appropriate post-processing device may be selected and an appropriate image forming standby time may be generated.
A bookbinding device for performing ring bookbinding is known. In this bookbinding device, punching processing is performed on a sheet or a sheet bundle by using a punching unit, and stitching processing is performed on punched holes with ring members by using a stitching unit, thereby performing ring bookbinding. This bookbinding device includes a unit for changing a sheet-bundle interval, which is an interval between the last sheet of a preceding bundle and the first sheet of a subsequent bundle, between a first mode in which punching processing and stitching processing are performed and a second mode in which only punching processing is performed. With the provision of this unit, the sheet-bundle interval can be set in accordance with the type of mode, that is, the first mode or the second mode, thereby improving the usability and the productivity when the two modes are used at the same time.
An image forming apparatus including the following post-processing device is also known. The post-processing device includes a post-processing unit that performs post-processing on a plurality of sheets on which images are formed, a post-processing calculator that calculates the timing at which an image will be formed on a sheet to be subjected to post-processing in accordance with the content of the post-processing which has been set in the image forming apparatus, and a timing informing unit that informs the image forming apparatus of the timing at which an image will be formed on the sheet, based on a calculation of the timing by the post-processing calculator. The image forming apparatus includes a post-processing setting unit that instructs a user to set the content of post-processing to be performed in the post-processing device, a post-processing-content informing unit that informs the post-processing device of the post-processing content which has been set by the post-processing setting unit, and a printer that forms an image on a sheet. The image forming apparatus also includes a sheet-position setting unit that sets a sheet at a predetermined position of the printer in accordance with the timing informed by the timing informing unit. With this configuration, since the image forming apparatus sets a sheet at a predetermined position of the printer in accordance with the timing informed by the timing informing unit, a sheet-bundle interval table is not necessary, and also, calculations which may be made by considering operating conditions in the image forming apparatus are not necessary. As a result, a sheet-bundle interval table can be omitted, and also, it is possible to provide an image forming apparatus including an easy-to-control post-processing device that can optimize the sheet-bundle interval.
In the above-described first post-processing device, for feeding a sheet of a subsequent bundle, the stapling operation time of an immediately preceding sheet bundle is utilized. In actuality, however, measurements of the stapling operation time of the immediately preceding sheet bundle have not been made in time before a sheet of a subsequent bundle is fed. This is due to the fact that, at the time when the stapling processing has finished, it is necessary that the first sheet of a subsequent sheet bundle have already reached the post-processing device.
Moreover, normally, the stapling operation time may vary, for one stapling operation, from several milliseconds to several tens of milliseconds depending on the type of sheet. The first sheet processing device, the second sheet processing device, the image forming system, the bookbinding device, and the image forming apparatus are not able to handle such a change in the stapling operation time occurring when the type of sheet is changed.
One of the setting conditions including the above-described stapling processing is a bookbinding processing condition that punching processing be performed all sheets forming a sheet bundle and stapling processing be performed all the punched sheets.
For both the stapling processing and punching processing, a brushed DC motor is used, and power is supplied to the brushed DC motor by using a low voltage (for example, 24 V). In both the stapling processing and punching processing, sheets are passed through by using a certain member. When stapling processing and punching processing are performed at the same time, the operating environment temperature is the same. Accordingly, if the time to perform punching processing is measured, it is possible to estimate the time to perform stapling processing by taking these factors into consideration. Then, if the feed timing (sheet-bundle interval) at which a sheet of a subsequent bundle will be fed is set based on the estimated time, the sheet-bundle interval time may be optimized in accordance with the type of sheet, and the entire bookbinding processing time may also be decreased.